1. Field of the Invention
This invention relates to an illumination system for endoscopes which are widely used in the field of medicine, and in particular, to a rigid endoscope used in the field of surgery.
2. Description of Related Art
Recently, a minimally invasive surgery using an endoscope and special treatment tools has been popularized in the field of surgery of medicine. A disease for which an abdominal operation has been required in the past has come to be treated by the minimally invasive surgery under the endoscope. Thus, in order to relieve social burdens of patients, for example, by reducing the term of hospitalization, it is expected that a surgical operation under the endoscope will be widely developed in the future.
In the surgical operation under the endoscope, the following requirements are now desired.
(1) Reduction in diameter of an endoscope for further promoting the minimally invasive surgery PA1 (2) Establishment of an operating room for the exclusive use of the endoscope in which medical instruments can be integrally controlled, without using cables
For item (1), a further minimally invasive surgery can be promoted by diminishing the diameter of the endoscope, and the social burdens of patients can be greatly relieved by further reducing the term of hospitalization.
As for item (2), at least 7-8 kinds of instruments are used nowadays for the surgical operation under the endoscope, which is performed by connecting these instruments by tubes or cables.
In a conventional operating room in which the surgical operation under the endoscope is performed, however, as mentioned above, a number of tubes or cables are provided which are means for connecting individual instruments with treatment tools, and they are crossed and extended across a sanitary region and a non-sanitary region, without distinction.
Although conventional instruments used for manipulation employing the endoscope are available in about 10 kinds, individual instruments are all controlled by themselves and thus a systematic work efficiency is considerably impaired. In particular, in the operating room, a plurality of instruments are arranged in disorder around an operating table, and this situation gives rise to the problem that their control is extremely difficult.
In this way, the operating room for the exclusive use of the endoscope stated in item (2) is urgently required, in which instruments including a light source are arranged at some distance away from the operating table. Light emitted from the light source is transmitted to a centralized connector lying on the side of the operating table by a connecting light guide through a ceiling, and the centralized connector has a role like a secondary light source. The establishment of the operating room for the exclusive use of the endoscope eliminates a complicated crossing of tubes or cables around the operating table and enables an operator to devote himself to the surgical operation under circumstances of safety and good work efficiency.
However, the greatest of anxieties for achieving the requirements of items (1) and (2) is that the surgical operation under the endoscope becomes difficult because of a shortage in the amount of light.
As shown in FIG. 1, an illumination system of a rigid endoscope used for the surgical operation under the endoscope is provided with a light guide 1 on the scope side, receiving light emitted from a light source 8 to irradiate an observation part with the light. On the other hand, an observation system thereof includes an objective lens 2 receiving the light from the observation part to form an optical image, a relay lens 3 transmitting the optical image to an eyepiece section, and an eyepiece 4 for magnifying and observing the optical image transmitted by the relay lens 3.
The sectional area of the inserting section of the rigid endoscope is mostly occupied by the light guide 1 on the scope side and the relay lens 3. Thus, in order to diminish the diameter of the rigid endoscope, it is necessary to reduce the number of fibers of the light guide 1 on the scope side or diminish the outside diameter of the relay lens 3. However, a reduction in the number of fibers of the light guide 1 on the scope side causes the amount of light for irradiating the observation part to be decreased, while diminishing the diameter of the relay lens 3 means that the amount of light received from the observation part is reduced.
Consequently, for example, when a rigid endoscope with an outside diameter of 10 mm is reduced to 3 mm, its sectional area is decreased to less than 10%, and thus the sum of the amount of light which can be transmitted by the light guide and that of the amount of light received by the observation system are also decreased at almost the same rate.
In the operating room for the exclusive use of the endoscope, the connecting light guide with as long as 10 m or more, extending from the light source to the operating table, is used to transmit the light. As such, with this connecting light guide, the amount of light is diminished to less than 30% because the light is absorbed by the material of fiber cores of the connecting light guide. Moreover, where the numerical aperture (NA) of the connecting light guide is low, a loss of the amount of light becomes more prominent. If the connecting light guide is a multi-fiber, the loss of the amount of light will be further caused at the entrance section of the light guide because the core share of the light guide is small.